1. Field of the Invention
The invention relates to a process for preparing aminoglycol by reacting ketoximes with ethylene oxide under basic conditions to give a substituted 2-hydroxyethyl ketoxime and subsequently reacting the latter with an acid to give aminoglycol.
2. Description of Related Art
Aminoglycol is an important synthesis unit for preparing herbicidally active agrochemical ingredients, especially for preparing dioxazine derivatives, especially dioxazinylpyridinylsulfonylureas (U.S. Pat. No. 5,476,936).
For instance, EP0655437 teaches a process for preparing aminoglycol by reacting acetone oxime with ethylene carbonate in the presence of DBU, but only conversion yields of 65-75% are achieved. In addition, DBU is an expensive feedstock which cannot be recovered.
U.S. Pat. No. 4,687,849 proposes a process for preparing 2-(isopropylideneamino)-oxyethanol, in which acetone oxime in water is reacted with ethylene oxide. A reaction yield was not reported. The 2-hydroxyethyl acetone oxime product has a very good water solubility and is difficult to isolate by extraction. However, reworking the reaction route specified in U.S. Pat. No. 4,687,849 (example 1) shows that the yield of this reaction does not exceed 50-55%, since the alkylation of nitrogen and the formation of nitrone take place as side reactions. Nitrones are highly undesired by-products since they decompose even in the course of workup, and their isolation is undesired owing to the high decomposition potential.
A further method for preparing aminoglycol (J. Chem. Soc. Chem. Com., 1986, 903) proceeds from 2-bromoethanol and N-hydroxyphthalimide and subsequent cleavage with hydrazine hydrate, which, however, is associated with very high production costs.
It can thus be stated that the processes described in the prior art have the disadvantage that either (a) they are very expensive and/or (b) the yields are not high enough to implement this reaction step industrially and/or (c) the desired aminoglycol cannot be removed and isolated from the reaction by-products in a simple and inexpensive manner.